Pressure-actuated electric control device



July 19, 1927.

Filed Nov. 9. 1925 /ldnlfllfnfrnnillnlrdflal INVENTOR. )7u @z-ATTORNEYS.

Patented July 19, 19277.

' UNITED STATES PATENTl OFFICE.

IRA E. MCCABE, 0E, CHICAGO, ILLINOIS.

PRESSURE-ACTUATED ELECTRIC CONTROL DEVICE.

' Application led November 9, 1925. Serial No. 67,796.

This invention relates to improvements in electric control ydevices andmore particularly to a pressure actuated electrical control device.

In many instances electrically operated devices are employed in theproduction of heat and in the electric circuit of such a device it isdesirable to provide a control for starting and stopping the operationof such a device which control is operated by the temperature created bythe operation of the device.

It is an object of this invention to provide a device of this character,and an embodiment of this device is particularly illustratedanddescribed as adapte-d for use in an electrically operated furnace orheat producing device particularly used as a part of an electricallyoperated liquid fuel burner system for domestic purposes, although thisinvention contemplates other uses of this control. It is av furtherobject to provide a device of this character which is particularlyadaptedh in electrically operated domestic liquidy fuel burner systemstp act as a safety device for such systems.

l/Vhile a preferred form of this invention is illustrated on theaccompanying sheet of drawing, yet it is to be understood that minordetail changes may`be made therein without detracting from the scope ofthe invention.

In the drawings:

Figure 1 is a view in frontelevation ofa preferred form of this device,with the casing cover removed and partly in section.

Figure 2 is a view in end elevation of Figure 1 with parts broken awayand with parts in section.

In the embodiment f this invention illustrated, the circuit to the motoris closed or opened by the tiltin movement of the mercury switch 1, whicis shown mounted on a pivoted carrier plate 2, with two terminalsadjacent each other and near one end of the tube so that when the tubeis tilted in that direction the mercury within the tube will accumulatein that end and close the circuit through said terminals,` and whentilted in the opposite direction the mercury will` flow away from theterminals and break the circuit therethrough. The tilting plate carryingthe mercury tube is provided with a counterweight 3 which will normallytilt the tube to the open or circuit-breaking position. The plate 2carrying the mercury tube is also provided with a depending projectionin the form of a pawl 4, adapted to engage' in the teeth of a ratchetwheel 5 carried by a sleeve 6, having a detachable connection with anenclosed fixed shaft 7, whereby the mercury tube switch may be tiltedinto the @closed position and held against the counterweight byengagement of the pawl with the ratchet and which when the ratchetcarrying-sleeve becomes detached will allow the counter weight to causethe ratchet to be rotated by the pa'wl releasing the tilting plate 2 andtilt the switch into the open posltion.

The sleeve 6, carrying the ratchet wheel 5, is of greater inner diameterthan the outer diameter of the fixed shaft 7 which it surrounds.y Thespace between the inner circumference of the sleeve and the outercircumference of the shaft is filled with solder vwhich will normallysecure the sleeve `in The shaft 7, is-

.in a cylinder 11 of lavite or other electric insulating material withthe disc at one end bearing against the heat transmitting bracket 9, andthe other end bearing against a movable block 12, -held in place andmovable in the lavite cylinder. Three posts 13 secure the heattransmitting bracket Q to a closure plate 14 beyond the movable block. Asheet' ofv This mica or other electric insulating material f capable oftransmitting heat is interposed between the series of gra hite disksandheat transmitting bracket an between the series of graphite disks themovable block. The closure plate 14 supported onl the posts 13aextending from the heat transmitting bracket is provided with anaperture 15 concentric with the graphite disks 10 'in which aperture ismounted a sleeve 16 having an outstanding flange 17 about its exteriorend. l

The interior of the sleeve is screw-threaded and adapted to registerwith a' similarly screw-threaded Japerture in the movableY block 12. Asimilarly screw-threaded pivot 18 having a flat head or button 19 isthreaded through the sleeve and into the block securing the two togetherwhereby the movement of the block limited by the plate 14 in onedirection and by the sleeve flange 17 in the vother direction. The heattransmitting bracket is carried upon and insulated from an outstandingarm 20 of a supporting plate 21 secured to the rear of the instrumentcasing. Upon this plate 21 below the graphite disks a pressure applyingmember 22 is pivotally ,mounted having a portion 23 'adapted to contactwith the flat head or buta tube 28 leading therefrom to a heat coil orbulb 29 adapted to be' secured within the stack 30 leading from thefurnace to the chimney. or otherwise located so that the heat generatedin the furnace by the flame from the electrically operated voil burnermechanism will cause an expansible gas or liquid within the bulb 29.tube 28 and Bou'rdon tube 26 to exert and vary the pressure thereincausing the Bourdon tube to expand or contract.

The free endof the Bourdon tube 26 is pivotally connected by anoperating link to the pressure applying member 22, preferably with anadjustable connection thereto, such as the slot illustrated, so thatupon the expansion of the Bourdon tube pressure will be applied to theseries of .graphite disks, the amount of pr ssure and the time ofapplication of the p1" sure being regulated by the distance between thehead or button '19 upon the shaftand the sleeveflange 17 by the screwingor unscrewmg of the threaded portion of the shaft 18 into the movableblock 12.

It is preferable to construct the operating link of two parts having aslidable fric` tional engagement with the other, such as by providingone part 31 with a reduced Aportion 32 adapted to be received and slidewithin a recessed portion 33 of the other member 34 having said recessedportion cut out on one side adapted to receive a spring pressed clampingmember 35 to bear with adjustable tension upon the reduced portion ofthe other member sliding within the recess, whereby an outward movementof the free end of the Bourdon tube, as the Bourdon tube expands, willbe transmitted through the operating link to cause the pressureapplyingmember 22 to move about its pivot and apply pressure upon theshaft 18 and thence through the movable block 12 to compress thegraphite disks 10 and when further movement of the shaft is limited bythe flange 17 on the sleeve engaging the plate 11 and extension 22stopping on lower limiting post 25,v further movement of the tree end oithe Bourdon tube will cause the reduced end portion 32 of theoperatinglink' continued inward movement of the free end thereof thereduced portion of one member of the operating link will be caused toover-- come the frictional engagement with the clamp and slide withinthe recess of the other member, whereby expansion of the Bourdon tube atany -time will immediately apply pressure to the graphite disks. l

The pawl 4, normally engaging the ratchet wheel 5 is so constructed thata pressure against the pawl in the direction of the back of the casing-will cause it to disengage from the ratchet and thereby allow thecounterweight 3 to tilt the mercury tube into the open position andbreak the circuit.l therethrough. A pawl releasing means is provided inthis dev ice which will break the circuit as the expansion of theBourdon tube reaches its danger limit and this-means comprises an arm 36pivoted at one end to the free end of the Bourdon tube which passes.over the horizontal portion of thepawl 4 when engaging the ratchet wheeland is provided with an angular depending portion 37 adapted ,as theBourdon tube approaches its danger limit, to engage and depress the pawl.4 to release it from the ratchet 5 and allow the counterweight to breakthe circuit. The free end of the pawlreleasing member 36 is providedwith an irregular slot 38 adapted to slide over a pin 39 to support thevarm 36 with the depending portion thereof out of contact with the pawlduring the normal operation of the Bourdon tube, but from the shape ofthe slot 38 adapted to present the depending portion`37 first into lineand then into engagement with the pawl 4 as the Bourdon tube approachesthe danger limit.

`The instrument casing is provided with three binding posts the upperbinding post 40 being connected to a lead 41 from the commercial sourceof current and to one terminal of the mercury tube switch. The otherterminal of the mercury-tube switch is connected to the middle bindingpost 42 which in turn is connected by a lead 43'to one of the outermostgraphite disks 10 of the series. The other outermost graphite disk ofthe series is connected by a lead 44 to the lowermost binding post 45which in turn is connectedto one plple ofthe electric motor M foroperating t e burner mecha# .nism and the other pole of the motor isvconnected to the other lead 46 of the commercial current.

In the electrical. art it is recognized that a series of graphite diskssuch as shown and described will transmit electricity and generate-heatin 'proportion to t-he ,amount of pressure applied to the end of suchseries. of disks, the greater the pressure, the greater the conductivityor ease with which the current passes through t-he series, as increasingthe pressure upon the series of disks decreases the electricalresistance therethrough and the heat generated by the resistance variesin direct proportion thereto. By a proper adjust-ment of the relationbetween the movable plate 12 and the screw-threaded shaft 18 an amountof pressure can be normally applied to the series of graphite disks togenerate heat sufficient to melt the solder normally securing theratchetwheel 5 in fixed relation to the fixed shaft 7 and by providing aproper number of graphite disks Asuliicient pressure may be appliedthereto by normal movement of the member 22 upon expansion of theBourdon tube 26 to allow the current to pass through the disks withoutgenerating suflicient heat to` melt the solder. The instrument is soadjusted that with the switch in closed posit-ion, as shown iugFigure 1,and the circuit through the motor closed, the current will pass throughthe mercury tube 1, and thence through the series of graphite diskslOwhich are so adjusted that a continuation of the passage of currentwill generate sufficient heat to melt the solder and release the switchto be operated by the counterweight 3 to break the circuit. The partsare also adjusted so that as soon as themotor starts the oil burner*mechanism operating, the flame therefrom or the heat arising from thefire box acting upon the bulb or coil 29 will cause an expansion of theBourdon tube 26- thus applying pressure through the link and pressureapplying member to t-he series of graphite disks reducing the generationof heatherein and the parts are further adjusted so that the normalexpansion of the Bourdon tube under these conditions will cause theflange 17 upon the sleeve to engage the plate 14 when the current passesfreely through the compressed graphite disks without generatingsuiiicient heat to melt the solder. A.

further expansion ofthe Bourdon tube will be accommodated by thefrictional engagement of the two sections 31 and 34 of the connectinglink without further movement of the pressure applying member. Upon thefailure of the burner iiame .from any cause the contraction of theBourdon tube Will immediately release the pressure from the graphitedisks thereby immediately increasing the heat generated therein to meltthe solder and release the switch toy assume the open position. If fromany cause the amount of pressure within the Bourdon tube approaches itsdanger limit, the sliding member 37 will engage the pawl and release itfrom the ratchet and allow the counterweight to break the circuit.

From the above description it is seen that this device includes a doublesafety device both of which depend upon the operation of the oil burnermechanism. The first safety device is operated by the commercial sourceof current passing therethrough causing the circuit to be broken in casethe burner flame fails to ignite or becomes extinguished for any reason.The second safety devicer will operate if the burner mechanism producesexcessive pressure within the' Bourdon tube causing it to expand andapproach this danger limit to release lthe pawl and allow thecounterweight to throw the switch to break the electric circuit. i

I claim:

1. In a pressure actuated electric control, an electric switch,meansnormally acting to hold the switch in open position, detachable meansfor holding the switch in closed position, an operating member thereforin circuit `with the switch and operable by variations in currentpassing therethrough to release said switch holding means, an expansibleand contractable member, means actuated thereby to cause variations inthe current passing through the operating member of the switch holdingmeans, and additional means operable thereby to mechanically detach saidswitch holding means. y

2. In a pressure actuated electric control,

an electric switch, means normally acting to hold the switch in openposition, detachable means for holding the switch in closed positionreleasable mechanically and upon the application of heat, an electricheat generating, means in circuit lwith said switch, an expansible andcontractable member,

means .actuated thereby adapted to produce variations in the heatgenerated by the electrio means to hold or release the detachable means,an additionalmeans actuated at Yal predetermined expansion thereof tooperate said mechanical releasing means.

3. In a pressure actuated electric control, an electric switch, meansnormally acting to hold the switch in open position, detachable lill)means for holding the switch in closed position releasable mechanicallyand independently upon application of heat, pressure controlled electricheat generating means in circuit `with the switch, an expansin ble andcontractable member, meansfassociated with said member and said heatgenerating means for transmitting pressure upon expansion andcontraction of said member to said heat generating means for controllinggeneration of heat thereby, and independent means operable at apredetermined expansion of said member to release said switch holdingmeans.

4. In a pressure actuated electric control, an electric switch, means`normally acting to hold the switch in open position, detachable meansholding the switch in closed position releasable mechanically andindependently upon the application of heat, pressure controlled electricheat generating means in circuit with the switch, an expansible andcontractable member, means operable upon the expansion and contractionof said member to transmit Variations in pressure to said .electric heatgenerating means to vary the degree of heat generated thereby and atpredetermined expansion of said expansible and'contractable means toreduce the amount of heat generated by said electric means, and at apredetern'iined greater expansion to mechanically release said switchholding means.

5. In a pressure actuated electric control, an electric switch, meansnormally acting' to hold the switch in open position, detachable meansfor holding the switch in closed position, said means adapted to releasethe switch by mechanical operation and additionally bythe application ofheat, pressur controlled electric heat generating means in circuit withthe switch adapted to release said detachable switch holding means, apressure actuated expansible and contractable member, means for applyingpressure therefrom to said pressure control electric heat generatingmeans, a connection between said means and said expansible andcontractable member normally allowing said electric means to generatesufficient degree of heat to detach said switch and upon expansion ofsaid expansible and contractablel member to apply pressure t0 saidelectric heat generating means to reduce the degree of heat therebelow,and means operable upon abnormal expansion of said expansible andcontractable member to operate said mechanical means to release saidswitch holding means.

lRA E. MCCABE.

